It's not really a boundary to state, you just have to live it.

If you have plans, don't change them for him unless you think it's really, really important for D8.

If you know something, communicate, don't assume. Like here, you say "I knew he would have plans to go out as he had no kids but figures having her would be more important!"

I would have asked, "But you don't have your own girls that night - do you want D8 then?"

M 16 yrs, WH62, P54
3 adult blended kids
EA 11/13, BD1 6/14
PA fall 14, BD2 2/15
Piecing 2015, BD3 12/15
Separated 4/16
WH moved OW in 5/16
Divorced 6/15/17